Many types of printing machines utilize folding apparatus in which the sheets or sheet units, for example superimposed layers of sheets such as superimposed newspaper sheets, are transported between belt transport systems having upper and lower belts. The output transport belt lines receiving the printed material from the printing machine operate at a first high speed; subsequent receiving belt transport systems operate at a lower speed. It is, therefore, necessary to provide an intermediate system to match the speed of the sheets received from the printing machine to the sheets which can be handled by the subsequent lower speed belt system.
German Published Patent Application DE-AS No. 27 50 592 describes apparatus in which sheets delivered from a folding cylinder, after a first fold, are supplied to a first belt transport system. They are then oriented and delayed with respect to a stop element which operates at a speed slower than the supply speed of the first belt line or system. The delayed and oriented elements, for example the folded sheets, are then transmitted to a second belt line which operates at a lower speed, which is associated with a folding knife to form a "third fold" which, actually, is a second longitudinal fold.
Arrangements of this type have the disadvantage that the sheets meet at high speed the stop element which operates at a lower speed; when the difference in speed exceeds a certain level, the folded high-speed sheets have a tendency to bounce backwardly or to misalign; if this is the case, the "third fold", actually the second longitudinal fold, will no longer be carried out with sufficient accuracy.